Neutron generator

ABSTRACT

Neutron generator with an ion source at high voltage potential for the generation of an ion beam and a target in which neutrons are generated by the ion beam through nuclear reactions.

United States Patent Gesellschait Fuer Kernforselmng mbll Karlsruhe, Weberstr, Germany [73] Assignee [32] Priority Dec. 21, 1968 [33] Germany [3|] P18164595 {54] NEUTRON GENERATOR [5 l] Int. Cl 621g 3/04 [50] Field of Search 250/846; 313/61 63 [56] Relerences Cited UNITED STATES PATENTS 3,371,238 2/l968 Beckurts et al 250/845 X Primary Examiner-James W. Lawrence Assistant Examiner-Davis L. Willis Att0rneySpencer & Kaye Chin's, 5 Drum" gm ABSTRACT: Neutron generator with an ion source at high voltage potential for the generation of an ion beam and a tar- U-S. o g i neutrons are g t d th i b th gh 313/6 S nuclear reactions.

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NEUTRON GENERATOR SPECIFICATION Neutron generators are neutron physics instruments of which, for the time being, only relatively small numbers are needed and which represents a considerable value. In addition, these instruments must be adapted again and again to very specific purposes, especially for research work in the field of nuclear physics, and they require designs of one or more components which satisfy these requirements optimally.

This requires considerable financial expenditures which, in turn, limits to a minimum the application of neutron generators.

Neutron generators are known in which the ion source is maintained at high voltage potential and is connected to the opening of an evacuated housing.

Moreover, neutron generators are known in which an electrode at high voltage potential is suspended in an evacuated housing kept at ground potential so as to be insulated.

It is the objective of the invention to create a neutron generator which is versatile in use and can be optimally adapted to very different purposes in an economic way.

In the invention, this problem is solved by combining the ion source as one unit in a rotational symmetrical ion source housing supported by several insulators, which contact the ion source housing radially and are directed perpendicular to the ion beam, and enclosed on all sides by the metallic vacuum housing at ground potential at whose side opposite the ion exit opening a flange is attached for the optional connection of component groups containing target holders and electrodes for suction and/or focusing of the ion beam adapted to the specific objectives. 1

In this design, it is useful to provide for the ion source to be supported by two insulators one of which is connected firmly with the vacuum housing and in a detachable way with the ion source housing and the other is connected firmly with the ion source housing and in a detachable way with the vacuum housing; the unit consisting of ion source housing and insulator can be withdrawn from the vacuum housing laterally.

The current-carrying capacity of the ion source is increased by liquid cooling, the ion source being fed an insulating liquid coolant through a bore in the support insulator.

For feeding deuterium gas to the ion source a gas reduction valve is installed at the end of the removable insulator facing away from the ion source; this valve is connected with the ion source by a metal pipe carried through the insulator and is fed deuterium gas through an electrically insulating tube.

A group of components consisting of a suction electrode and a target holder can be connected to the vacuum housing surrounding the ion source; in this case, the suction electrode and target holder are at ground potential. It is possible also to design the target as a rotary target. If a larger distance is required between the ion source and the target with the target size predetermined, an electrostatic lens system for focusing the ion beam and an ion tube to accommodate the target can be flanged onto the vacuum housing.

If a higher voltage is to be applied to the ion source, it is advantageous to envelop the ion source in a sheet metal sleeve suspended so as to be insulated whose potential is below that of the ion source. It is possible also to connect the sheet metal sleeve electrically with a lens electrode.

Another possibility of variation consists in the connection to the vacuum housing surrounding the ion source of a suction electrode at ground potential and a target housing suspended in a vacuum housing so as to be insulated and maintained at a negative high voltage. The ions entering the target housing are already preaccelerated in this arrangement so that the ion energy is doubled while the difficulty of doubling the ion source voltage is avoided. In case a larger distance is required between the accelerator and the target, a focusing system with adjustable lens voltage can be installed between the ion source and the target.

For an additional increase in ion energy a voltage modulated with a high frequency by the principle known from linear accelerators is applied to the electrode system accelerating the ions in the direction of the target.

The ion source may be equipped also with a coil instead of a permanent magnet to generate the magnetic field. In this case, it is advantageous to feed this coil from the filament circuit of the ion source at high voltage potential. The AC voltage taken from the filament transformer is rectified and controlled by a final control element arranged in the connector block of the supply lines. This arrangement saves a buffer transformer which otherwise would be required for the power supply of the 1011 source.

Examples of the embodiment of the invention are shown in the drawing and will be described in greater detail below:

FIG. I shows an ion source in a vacuum housing,

FIG. 2 a neutron generator with a grounded target holder,

FIG. 3 a neutron generator with a focusing device and an ion source enveloped by the control electrode,

FIG. 4 neutron generator with a target holder at negative high voltage potential,

FIG. 5 a neutron generator with a focusing device and a target holder at negative high voltage potential.

In FIG. I, the ion source 1 is supported by the insulators 2 and 3. Insulator 2 is spring clamped in the vacuumhousing 4 enclosing the ion source and is pressed into a seat of the ion source housing 5. The insulator 3 is firmly connected with the ion source housing 5. This unit consisting of the ion source housing, insulator, and support flange 401 can be removed from the vacuum housing laterally after unscrewing the flange connection. The ion source 1 is surrounded by the metallic housing 5 which has an ion exit opening 501 and a cover 502. After removal of the cover 502 the cathode flange 101, which is sealed against the housing 5 and the cooling channel 102 by a sealing ring 103 and carries the cathode, can be removed for replacement of the cathode without the liquid coolant having to be discharged.

In the central bore 301 of the insulator 3 there is a stainless steel pipe 302 carrying the anode voltage which is run through the conical connector 303 consisting of insulating material. For supply of deuterium gas to the ion source an insulated copper pipe 304 is carried through the pipe 302 which is connected to the cathode flange on one side and to a needle valve 305 controlled by the gas pressure or mechanically on the other side.

Moreover, there is a cable 306 inside the pipe 302 which is used to supply the filament current to the cathode together with the copper pipe 304. The copper pipe 304 and the cable 306 carry also the current necessary for maintaining the plasma, which current is discharged through the anode and the pipe 302.

For the power supply of the intermediate electrode 105 an insulated cable 307 is run through the pipe 302 which is connected to familiar circuit elements.

Pipe 302 contains also a tube 308 for removing the liquid cooling the ion source. The liquid coolant is supplied through the residual cross section of the pipe 302.

A connecter block 309 of insulating material is put upon the conical connecting piece 303 so as to be oiltight. For supplying the ion source with high voltage, pulsed voltage and heating current there are plug-and-socket connections in the connector block 309 which are not shown here, the high voltage being fed through a cable, the supply voltages of the ion source through transfonners not shown.

The needle valve 305 is set by means of an insulating bar and is supplied deuterium gas through an insulating tube. In the connector block 309 also channels for the coolant supply not shown here are provided for.

It is possible to connect a high-vacuum pump to the flange 402 of the vacuum housing 4 surrounding the ion source I and to connect to flange 403 units containing target holders and electrodes for suction and/or focusing of ion beams adapted to specific purposes.

in H6. 2, a group of components is flanged to flange 403 of the vacuum housing 4 which comprise a suction electrode 6 at ground potential and a target holder 7 with a target 8. The distance of the target from the input plane of the ions into the bore of the suction electrode may be, e.g., 100 to 200 mm. with a target diameter between 30 and W mm. The target holder is equipped with gas or liquid cooling.

Instead of the stationary target it would be possible also to install a rotary target not shown.

In FIG. 3, the connection of another group of components containing the focusing system 9 is shown. In this case, e.g., the ion source 1 carries a positive high voltage of about 150 Kv., the lens electrodes 901 carry a positive high voltage of some 100 Kv., and the lens electrode 902 carries a voltage which may be varied, e.g., between -30 Kv. and +30 Kv.

To be able to apply a higher voltage to the ion source, the ion source housing is enclosed by a sheet metal shell 10 suspended so as to be insulated the potential of which is below that of the ion source. This sheet metal wheel may be connected, e.g., to the lens electrode 91 so as to be conducting.

in FIG. 4, another group of components is attached to flange 403 in which the target is arranged inside a vacuum housing 11 so as to be insulated and is at negative high voltage potential. The suction electrode 6 is at ground potential, the ion source 1 at positive high voltage potential. This results in a doubling of the ion energy while avoiding the difficulties which would arise if the ion source voltage were doubled and the target put at ground potential.

The target housing is held by two support insulators l2, l3 contacting it laterally. The high-voltage cable 14 is carried through the insulator l2, and through bores 15 in the insulator 13 the liquid coolant for cooling the target is fed in and removed.

Also in FIG. 5, the target is at a negative high voltage potential and is suspended in a vacuum chamber so as to be insulated. Because of the larger distance required between the ion source and the target a focusing system 9 with an adjustable lens voltage is provided. The target holder 7 with the target 8 is arranged in an ion tube 16. The ion tube is enclosed in a housing 17 at ground potential which is connected to the housing 18 of the focusing system so as to be vacuumtight.

The advantages gained from the invention consist especially in the possibility of optimally adapting neutron generators to different purposes in an economic way and at markedly less expense than before so as to expand the possibilities of their use greatly. This is connected also with an increase in operational safety and ease of handling.

I claim:

1. Neutron generator with an ion source kept at high voltage potential and arranged inside a vacuum housing so as to be insulated for generating an ion beam, and a target in which the ion beam produces neutrons through nuclear reactions, the ion source being combined as one unit inside a rotation symmetrical ion source housing supported by several insulators radially contacting the housing of the ion source and directed perpendicular to the ion beam, and surrounded on all sides by the metallic vacuum housing at ground potential at whose side opposite the ion exit opening a flange is arranged for the optional connection of component groups which contain target holders and electrodes.

2. Neutron generator as claimed in claim 1 with an ion source supported by two insulators one of which is connected firmly with the vacuum housing and detachably with the ion source housing and the other of which is connected firmly with the housing of the ion source and detachably with the vacuum housing, and with the unit formed by the housing of the ion source and the insulator being laterally removable from the vacuum housing.

3. Neutron generator as claimed in claim 1 where the ion source is cooled by an insulating liquid through channels in the insulator.

4. Neutron generator as claimed in claim 2 with a gas reduction valve for feedin deuterium as to the ion source arranged at the side of t e removable insulator facing away from the ion source which valve is connected with the ion source by a metal pipe carried through the insulator and supplied with deuterium gas through an electrically insulating tube.

5. Neutron generator as claimed in claim 1 with a group of components consisting of a suction electrode and a target holder attached to the flange, the suction electrode and the target holder being at ground potential.

6. Neutron generator as claimed in claim 5 in which said target is a stationary target.

7. Neutron generator as claimed in claim 5 in which said target is a rotary target.

8. Neutron generator as claimed in claim I in which an electrostatic lens system for focusing the ion beam and an ion tube for accommodating the target are connected to the flange.

9. Neutron generator as claimed in claim 8 in which an electrostatic lens system and an ion tube at negative high voltage potential for accommodating the target are attached to the flange and the ion tube is enclosed by an evacuated cladding tube connected with the housing at ground potential of the lens system.

10. Neutron generator as claimed in claim 1 in which the ion source is enclosed by a sheet metal sleeve, supported so as to be insulated, the potential of said sleeve being below that of the ion source.

11. Neutron generator as claimed in claim 10 said sheet metal sleeve being electrically connected with one of the electrodes of the focusing system.

12. Neutron generator as claimed in claim 1 with a suction electrode at ground potential and a target housing suspended in a vacuum housing so as to be insulated and kept at negative high voltage attached to the flange.

l3. Neutron generator as claimed in claim 1 in which a voltage modulated by high frequency is applied to the electrode system accelerating the ions in the direction of the target.

14. Neutron generator as claimed in claim 1 with a duoplasmatron as the ion source in which a coil arranged in the ion source and generating the magnetic field is fed from the filament circuit of the ion source. 

1. Neutron generator with an ion source kept at high voltage potential and arranged inside a vacuum housing so as to be insulated for generating an ion beam, and a target in which the ion beam produces neutrons through nuclear reactions, the ion source being combined as one unit inside a rotation symmetrical ion source housing supported by several insulators radially contacting the housing of the ion source and directed perpendicular to the Ion beam, and surrounded on all sides by the metallic vacuum housing at ground potential at whose side opposite the ion exit opening a flange is arranged for the optional connection of component groups which contain target holders and electrodes.
 2. Neutron generator as claimed in claim 1 with an ion source supported by two insulators one of which is connected firmly with the vacuum housing and detachably with the ion source housing and the other of which is connected firmly with the housing of the ion source and detachably with the vacuum housing, and with the unit formed by the housing of the ion source and the insulator being laterally removable from the vacuum housing.
 3. Neutron generator as claimed in claim 1 where the ion source is cooled by an insulating liquid through channels in the insulator.
 4. Neutron generator as claimed in claim 2 with a gas reduction valve for feeding deuterium gas to the ion source arranged at the side of the removable insulator facing away from the ion source which valve is connected with the ion source by a metal pipe carried through the insulator and supplied with deuterium gas through an electrically insulating tube.
 5. Neutron generator as claimed in claim 1 with a group of components consisting of a suction electrode and a target holder attached to the flange, the suction electrode and the target holder being at ground potential.
 6. Neutron generator as claimed in claim 5 in which said target is a stationary target.
 7. Neutron generator as claimed in claim 5 in which said target is a rotary target.
 8. Neutron generator as claimed in claim 1 in which an electrostatic lens system for focusing the ion beam and an ion tube for accommodating the target are connected to the flange.
 9. Neutron generator as claimed in claim 8 in which an electrostatic lens system and an ion tube at negative high voltage potential for accommodating the target are attached to the flange and the ion tube is enclosed by an evacuated cladding tube connected with the housing at ground potential of the lens system.
 10. Neutron generator as claimed in claim 1 in which the ion source is enclosed by a sheet metal sleeve, supported so as to be insulated, the potential of said sleeve being below that of the ion source.
 11. Neutron generator as claimed in claim 10 said sheet metal sleeve being electrically connected with one of the electrodes of the focusing system.
 12. Neutron generator as claimed in claim 1 with a suction electrode at ground potential and a target housing suspended in a vacuum housing so as to be insulated and kept at negative high voltage attached to the flange.
 13. Neutron generator as claimed in claim 1 in which a voltage modulated by high frequency is applied to the electrode system accelerating the ions in the direction of the target.
 14. Neutron generator as claimed in claim 1 with a duoplasmatron as the ion source in which a coil arranged in the ion source and generating the magnetic field is fed from the filament circuit of the ion source. 